The word "dinosaur"
comes from the ancient Greek words
"deinos" ("terrible") and "sauros"
("lizard"). Strictly speaking, dinosaurs refer to land dwelling
creatures that dominated life on earth during the Mesozoic Era (225 million
to 65 million years ago). They lived alongside with marine reptiles (such
as ichthyosaurs, mosasaurs, plesiosaurs) and flying reptiles. As
a group, dinosaurs existed for over 150 million
years, occupying every type of environment and climate on Earth.
They ranged in size from those as small as a chicken to others over 100
feet long and weighing nearly 100 tons. Dinosaurs did not achieve their
great size or domination overnight - they evolved alongside reptiles and
mammals, but managed to outcompete them. Were it not for the great Cretaceous
extinction 65 million years ago, the mammals would not have evolved as
they did, nor would human beings as we know them exist.

The word dinosaur
is a very broad classification (like the word mammal) for many animals
which may be only distantly related (for example, the elephant and
the mouse are both mammals). They may be classified according to
their anatomy, using their hip bones, yielding 2 groups: (1) Saurischia
(lizard-hipped), and (2) Ornithischia
(bird-hipped).

Animals, including dinosaurs,
may also be classified by their mode of feeding. An herbivore eats
plants, a carnivore eats meat (usually plant eaters), and an omnivore
eats both plants and meat.

MAJOR DINOSAUR
GROUPS & GENERALIZED DESCRIPTIONS(Click group names below
to see sample images)

Ceratopsians:
large, heavy, powerful, fierce, plant eaters characterized by one or more
horns on the face (on the nose and/or over the eyes) and a bony shield
protecting the neck (Examples:
Monoclonius, Styracosaurus, Triceratops)

A
BRIEF HISTORY OF THE CHANGING CONCEPTIONS OF DINOSAURS

Pre-1800: In China, dinosaur bones
were called "dragon bones" and were ground up as medicine. In Europe and
America, they were thought to be unfortunate victims of the Great Flood
(apparently the Ark was all booked up).

Early 1800's: Dinosaur bones were
compared with those of modern reptiles, and they were declared to be extinct
reptiles, essentially, over-sized lizards. The reconstruction of them as
sprawling, slow moving, lizards persisted for many years. In fact, the
word "dinosaur" means "terrible lizard."

Circa 1870: American fossil hunters
E.D. Cope and O.C. Marsh were great rivals vying for lucrative publicity
from big-name museums such as Carnegie and American Museum of Natural History.

"WRONG-HEADEDNESS"
AFFECTED MAN AND DINOSAUR ALIKE

The bitter rivalry between former partners
Cope and Marsh was legendary. Their respective crews engaged in combat
in the field, and they often sabotaged each other's fieldwork. In the rush
to be the first to assemble the great dinosaur finds from fossil beds in
the Upper Jurassic rocks of Colorado, a skeleton of Brontosaurus
at the American Museum of Natural History in New York was given the wrong
head (which belonged to Camarasaurus, a stockier cousin), a mistake
which stood unchanged for nearly one hundred years!

Early 1900's: Charles Knight
murals are painted in the Paleontology Halls of the Field Museum. Some
of the scenes depicted include bulky sauropods (Brontosaurus) dragging
their tails in a swampy, lake environment. Recent evidence suggests that
Brontosaurus
(now called Apatosaurus) did not drag its tail on the ground, was
not as bulky, and probably lived near forests rather than swamps.
HOLLYWOOD, THE DINOSAUR MYTH-MAKER:
1930's - 1950's

Hollywood established humans and dinosaurs
as contemporaries in many films, bridging a gap of some 60 million years.
"One
Million Years B.C." (1966) extended the existence dinosaurs to the
Pleistocene, while "Godzilla" (1956) established new and impossible
sizes (200 feet tall) for carnosaurs. The "Flintstones" depicted dinosaurs
as beasts of burdens and "living appliances." Barney the Dinosaur is a
fixture in childrens' entertainment.

BRINGING DINOSAURS
UP TO DATE: 1960's -> Present

The largest and best-preserved Tyrannosaurus
rex skeleton is found in South Dakota - nicknamed "Sue" and debuts
as a blockbuster display at Chicago's Field Museum on May 17, 2000.

Tyrannosaurus rex is eclipsed as the
largest predator by the discovery of even larger, but unrelated dinosaur
predators such as Spinosaurus (seen in the movie Jurassic
Park III), and Giganotosaurus

Dinosaur anatomy has been corrected - dinosaurs
are now shown walking upright on erect limbs instead of sprawling with
limbs out and bent. [See "Jurassic Park" (1992)]

Dinosaur egg nests and juvenile skeletons
found - Jack Horner proposes that duckbill dinosaurs raised and
cared for their young, and lived in communities with other species (ceratopsians)
for self protection. Evidence of rapid growth rate in young dinosaurs suggests
warm-bloodedness. (1980)

Eoraptor skeleton found (earliest
known dinosaur) in Argentina, age
dated at 230 million years (1991)

NEW
& DIFFERENT (MODERN) VIEWS OF THE DINOSAURS

DINOSAURS - WHY
ARE THEY SUCH A BIG DEAL?

Primarily because they were big
- they were the largest and most successful land animals ever to live on
the earth. Also, they enjoyed a remarkably long (over 150 million years)
reign as the dominant fauna - a close look at their past history reveals
that they were extremely successful animals.

WHAT DO DINOSAURS
REPRESENT TO THE GENERAL PUBLIC?

Children view dinosaurs with great fascination
because they are "safe monsters" and because their scientific names are
difficult to pronounce by their parents (which delights children greatly).

Adults who are interested in dinosaurs
probably had such an interest in their earlier childhood years. For the
majority of the public, dinosaurs are the large, monstrous skeletons on
display in museums representing untold eons ago. Yet, their conceptions
of dinosaurs as a group have probably been colored by Hollywood monster
movies, or by outdated dinosaur books aimed primarily at children. In the
business world, the word "dinosaur" has come to represent "cumbersome obsolescence"
(such as the old style, big, gas guzzling automobiles).

WHAT'S NEW WITH
THE STUDY OF DINOSAURS?

Plenty - over the last few decades, a "dinosaur
renaissance" has been brought about by a new breed of paleontologists
looking at field evidence from many disciplines. They are looking at new
aspects of dinosaurs, such as their physiology, their lifestyles, their
childhood years, and their ecological relationships with each other. Also
being debated are previous assumptions of dinosaurs being cold-blooded
(ectothermic) and sluggish as modern reptiles are, and the various
extinction theories, which invoke some catastrophic cosmic events. Some
paleontologists have suggested that dinosaurs were the forerunners
of modern birds. The sheer volume of new dinosaur discoveries
has increased, as many finds are being reported in China, and in the U.S.
(Dinosaur National Monument in Jensen, Utah),
Texas (theropod footprints) and Arizona.
Extremely rare discoveries have included dinosaur juveniles, eggs, and
very early ancestral forms. The new image of dinosaurs is best seen in
the recent Hollywood cinema, such as the movie, Jurassic Park, which
was made in consultation with Jack Horner and Bob Bakker, two of the leading
dinosaur paleontologists of today.

IF DINOSAURS
DID SO WELL, WHY DID THEY DIE OUT?

The popular use of the word dinosaur implies
that they were "slow, lumbering, stupid beasts" who deserved to suffer
extinction as their fate before "superior mammals." Yet, scientific evidence
shows clearly that in direct competition with our mammalian ancestors,
the dinosaurs were the superior ones - they dominated the earth for twice
as long as the mammals, and were the most intelligent creatures of their
time. Yet the dinosaurs still became extinct, probably through no fault
of their own. The extinction of the dinosaurs
along with nearly one half of all species at the end of the Cretaceous
Period is one of the greatest scientific mysteries of all time. Since the
Alvarez theory was proposed in 1979, and much debated has ensued, most
scientists have come to accept the impact of a 6-mile
wide meteorite as the cause of the Cretaceous extinction; the leading
lines of evidence found at the Cretaceous-Tertiary
boundary include: shocked quartz crystals (stishovite,
a form produced only by very high-pressure impact), enrichment of iridium
(an element rare on earth, but common in meteorites), and widespread deposits
of soot (evidence of huge forest fires). The leading candidate
for the location of the impact crater is somewhere in the waters of the
Yucatan Peninsulan (near Chixulub) in the Gulf of Mexico, because there
is dramatic evidence of overturned late Cretaceous sediments caused by
a large impact in water. The debate over the details will still rage on
for years to come. The focus of dinosaur paleontologists is not "Why
did the dinosaurs become extinct?" but rather, "Why did they last for so
long?" Remember that mammals arose almost simultaneously with the reptiles,
yet lived in the shadow of the dinosaurs. Only the death of the dinosaurs
allowed mammals to fill the ecological vacuum. Some paleontologists believe
that were it not for some cosmic catastrophe, the dinosaurs would have
continued to evolve, and modern mammals (and man) may not have evolved
to their present form.

Luis & Walter Alvarez
stand before a rock outcrop showing the iridium anomaly at the Cretaceous-Tertiary
(K-T) time boundary